Valve lash - how do my numbers look?

Ok guys - did the valve lash on my 2004 wr450 for the first time in it's life (i know, I know :smirk: ). However, the bike had less than 10 hours on it (sat in a friends warehouse for years) until I bought it december of 2010. Since then I have put about 100 hours on the engine and figured it was time to check the lash before i was sorry....

anyway, here's what I got.

Intake valves

#1 - .005" - closest to the kick start lever

#2 - .004" - middle valve

#3 - .003" - closest to the cam sprocket

Exhaust valves

#4 - .008" - kickstart side

#5 - .008" - cam sprocket side

so, it seems like my #3 valve is just barely out of spec. I didn't have a shim kit so I buttoned it all back up, plan on checking them again in about 20 hours to see if they are moving. Any tips, words of advice, thoughts on what I found?

Also, how hard is it to do the actual shimming of the valves? I have never done that, but have built some v8 engines and have done valve lash using the number of turns method on rocker arm setups....figure the hardest part is re-aligning the cams?

What should I pick up as far as a shim kit goes to do the valve lash? yamaha dealer or is there a universal kit i can get that will have all the shims I will need for this and any future adjustments?



and yup, i do have the manual to walk me through all of it.....just wondering any tips or advice from those of you that have been at this longer than i have :smirk:

Well, you've got the manual, so it's alot easier with that helping for sure!! It's not all that difficult to do. The manual has a chart that will tell you what size shim you need to install to bring your bike into spec. That is, after you find out what shims your currently running! The most difficult thing about the whole process, is getting the cams in sync with each other. This is a pain because the cam chain is barely long enough. It can be done, but is time consuming. I also suggest writing down the shim sizes somewhere in your manual, so you have a permanent record. This way you always know what size shim needs to be installed next to get the bike back into spec, without having to tear it down to find out. Hope this helps! Maniac

It sounds like you have what you need to get the job done.

You can buy the shims per shim at the dealership, they might be $4-$8 each, depending on the dealer. You can buy a hotcams shim set off e-bay for about $75, but I think that's overkill for the average guy. I guess it depends on how far you are from the dealer, and how often you will need to be adjusting your valves.

You can buy shims from, in 0.025mm increments, for $1.50/ea.

I believe they only come in 0.050mm increments from Yamaha, but if your dealership also sells Honda, they should have the smaller increments.

Second that last suggestion; gets a pain in the ass to have to start measuring shims if the numbers rubbed off or werent stamped on in the first place

The manual pretty much covered it for me, and the maths is real simple:

As valves wear, they stick out of the head more and more, so you need slimmer shims each the time..

I work in metric, with metric gauges, shims etc.. The maths is easy that way.. If you want a 0.15 to 0.20 tolerance and your 0.15 gauge only just fits then you want to go up to a 0.20 by making a gap that is 0.05 bigger. So if there's a 1.60 shim in there, the shim needs to be 0.05 slimmer (to make a gap 0.05 bigger) so the shim 0.05 slimmer than a 1.60 is a 1.55..

Some people like the charts, some people do the maths

Draw a plan of the bike on paper. Put removed buckets on the paper so they can go back the same place they came out of:

Buckets O O


Intake O O O


Fill in..
Want = ..the clearance you want. Go for the upper clearance in the tolerance
Got = ..the clearance you measured now
Shim = ..with the size of your current shim
New = do WANT - GOT and write the RESULT, then do SHIM - RESULT

Put in the smallest shim available that is greater than or equal to your NEW value. E.g. if the NEW shim you need is a 169, install a 170

Want: 0.2
Got: 0.12
W-G: 0.08
Shim: 175
New: 1.75 - 0.08 = 167
167 shims don't exist in the yamaha line-up, so go for the 170


If your RESULT is negative, then you'll have to go up shim sizes rather than down.. Probably means someone shimmed it up wrongly last time

Remember that after calculating the shims you want, you might already have some, in other valves, so meet your wants, then look for a shim swap or purchase to meet the others. Remember to put the buckets back in the same holes they came out of, and don't drop dirt in the top of the engine

Other tips:

Use a magnet on a stick to remove the buckets and shims, much less chance you'll drop them inside the engine

The cam caps have a metal half moon circlip inside, don't drop that in the engine ieither

Follow all the advice from the manual about stuffing rags and hooking the chain to stop it dropping inside the engine

Loosen the spark plug if you dont have an auto decomp engine so you can turn it over easier

Turn the engine over slowly by hand through two full cycles of the flywheel. If it stops suddenly for any reason, don't force it, double check your valve timing

Check your clearances with the new shims after you turned everything over with a wrench a few times

Dont worry, when doing your timing, if the I beam on the flywheel isnt exactly on the mark when the cam cog marks are exactly in line with the head. So long as it's not a whole tooth out. On my YZ, when the Ibeam is aligned the exhaust cam dot is slightly above and the intake cam slightly below the head.. Just take note of how it is now

Put bolts back in the holes they came out of as soon as possible afte rthe part theyre securing is moved away - always handy for any kind of reassembly :smirk:

Digital camera pictures of the timing are massively handy when putting things back together..

Edited by cjard

thanks guys - all great help and great advice!

I'll get back at it on the next service and see just how hard this process is.

I'm a little confused by the statement that I will need slimmer shims, but i suppose I don't really know where the shims are yet until i tear it apart. I thought of it as "lifting" the cams with the shims, but sounds like the shim may be on top of the valve? again, this will be my first go around with valve lash on an engine that uses overhead cams. I'm not that old, but I always have owned v8 pushrod engines for my hot rods so that's what i know!

Yes, the shims sit on top of the valve, but under the valve bucket. When you install a thinner shim, you are basically moving the bucket farther away from the cam lobes, which gives you the necessary clearance. And like cjard said, make sure you put each bucket back in it's original location when finished. As you tear into it, everything we've said will make more sense. And if not, post a question and we'll try to help. Maniac

note, if you lift the buckets out with a magnet, the shim will probably be stuck inside it. Here's a diagram, 13 is the shim.. this is why they need to be slimmer, as valves wear away at the bottom they sit higher up, hence needing a slimmer shim


Edited by cjard

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